Protective cover system

ABSTRACT

Provided is a protective cover system including a first protective cover and a second protective cover, both include a polymer and being pre-formed into a curved shape so as to accommodate at least a part of a wind turbine blade to be protected, each of the first and second protective covers has a tip end and a root end, wherein the first protective cover includes a first overlap portion at the root end, and the second protective cover includes a second overlap portion at the tip end, wherein the shape of the first overlap portion is substantially complementary to the shape of the second overlap portion such that when overlapping the first and second overlap portions, the resulting cross section of the overlapped overlap portions substantially corresponds to the cross sections of the first or second protective covers outside the overlap portions.

The invention relates to a protective cover system for protecting aleading edge of a wind turbine rotor blade from erosion, to a windturbine rotor blade comprising such a protective cover system, and to amethod for mounting such a protective cover system to a wind turbinerotor blade.

Nowadays rotor or turbine blades e.g. blades for wind, gas or steamturbines are made of fibre reinforced plastic composite materials.Erosion of the leading edge of such blades is known to occur inoperation. Erosion of the leading edge of a turbine blade may reduce theefficiency of the blade and thus the power output by the turbine.

Wind turbine rotor blades, and in particular those of offshore windturbines, are specially affected by wear which occurs where interactingwith particles or droplets result in degrading of their leading edge.Erosion of the leading edge of wind turbine blades by dropletimpingement wear may reduce the blade aerodynamic efficiency and thusthe maximum output power of the wind turbine.

Erosion on a turbine blade may penetrate into the structural fibrereinforced laminate leading to severe failure of the turbine bladerequiring repair which can prove very costly to turbine operators. Thisholds especially true for offshore wind turbines because theirmaintenance costs are extremely high.

This is why generally a surface system is foreseen on the leading edgeof a wind turbine blade.

Repair procedures typically include a re-establishment of the surfacesystems mostly comprising filler and paint. In case of severedegradation, a lamination may be required. Different solutions are usedfor protecting and/or repairing leading edges of composite blades,including adhesive plastic tapes.

EP2497943 A1 discloses a wind turbine blade with an improved surface,wherein a plastic tape is arranged at specific locations of the blade toreinforce the blade surface.

The lift time of erosion protection tapes will last approximatelybetween 5-8 years, depending on the environmental conditions of thelocation of the wind turbine, as well as the turbine operatingconditions. In general an erosion protection tape will rupture due toheavy erosion, causing the layer left on the rotor blade to freelyflutter in the wind. This fluttering will result in a loss ofaerodynamic performance of the blade, as well as in the generation ofadditional aerodynamic noise.

Other solutions suggest erosion protection coatings applied by brush,roller, spatula or spray can. Generally, such coatings have to beapplied at a certain humidity level and within a special temperaturewindow, e.g. 20 and 25 degree Celsius. Thus, these solutions may not beused in the field, e.g. at offshore wind farms.

Further solutions suggest attaching a protective cap made of a polymermaterial to the forefront of a wind turbine blade during manufacturingof the blade. One drawback of these solutions is that due to the lengthof the protective cap needed for a larger wind turbine blade, themounting of such a protective cap in the field is impossible or at leastvery difficult, especially offshore. The transport and mounting of suchprotective caps are extremely cost intensive.

It is an object of the present invention to overcome the aforementioneddrawbacks. A further object of the present invention is to provide asolution which allows for significantly reducing the requiredmaintenance of the wind turbine and thus for reducing the maintenancecosts compared to known protective solutions.

These objects are solved by the features of the independent claims.Further advantageous developments are subject of the dependent claims.

The invention relates to a protective cover system (10) for protecting aleading edge (59) of a wind turbine rotor blade (55) from erosioncomprising a first protective cover (1) and a second protective cover(2). The first protective cover (1) and the second protective cover (2)comprise a polymer material. Both protective covers (1, 2) arepre-formed into a curved shape so as to accommodate at least a part of awind turbine blade (55). Each of the first and second protective covers(1, 2) has a tip end (3) and a root end (4).

The first protective cover (1) comprises a first overlap portion (4 a)at the root end (4) and the second protective cover (2) comprises asecond overlap portion (3 a) at the tip end (3).

The shape of the first overlap portion (4 a) at the root end (4) of thefirst protective cover (1) is substantially complementary to the shapeof the second overlap portion (2) at the tip end (3) of the secondprotective cover (2) such that when overlapping these first and secondoverlap portions (4 a, 3 a), the resulting cross section of theoverlapped overlap portions (4 a, 3 a) substantially corresponds to thecross sections of at least one of the first and second protective covers(1, 2) outside the overlap portions (4 a, 3 a).

The resulting cross section of the overlapped overlap portions (4 a, 3a) has and ensures a substantially continuous development of the crosssection throughout the first and second protective covers (1, 2). As aresult thereof, the aerodynamic properties of a wind turbine bladecomprising this arrangement correspond substantially to those comprisinga single protective cover with a continuous cross section developmentbetween its tip and root ends.

Smooth transitions between the first (1) and the second protective cover(2) are achieved when the protective cover system (10) is mounted on aleading edge of a blade (55).

An advantage thereof is that the protective cover system (10) does notpeel off and erosion of the blade may not arise or is extremely limitedwhere the protective covers (1, 2) overlap.

Advantageously, the protective cover system according to the presentinvention when mounted to a wind turbine blade avoids replenishing theleading edge protection of the wind turbine blade repeatedly during theoperational life of the blade. Tests have shown that the protectivecover system according to the invention may last on a wind turbine bladea lifetime of the blade.

In contrast to other erosion protection shields, like tapes or coatings,a protective cover (1, 2) of the protective cover system (10) accordingto the present invention do not only adapt to a curved shape of aleading edge of a blade when attached to the blade but it has the curvedshape already before being mounted to a curved surface. Thus thehandling of the protective covers (1, 2) during repair or manufacturingof blades (55) is easier than the handling of other erosion protectiveelements or shields like tapes or coatings. In addition, a tape couldhave the same Youngs Modulus, but not the same elongation at break as aprotective cover 1, 2 according to the present invention.

The shapes of the first and the second overlap portions (3 a, 4 a) aresubstantially complementary such that the protective cover system (10)has a substantially closed surface even if the overlap portions (3 a, 4a) do not engage with each other but only touch each other. Thus, incase the first and the second protective covers (1, 2) are disposed nextto one another and their overlap portions (3 a, 4 a) are disposed one ontop of the other but not as close as possible, a very little recess willarise on the surface of the protective cover system. However, due to thesubstantially complementary shapes of the overlap portions (3 a, 4 a),the protective cover system (10) has no interruption and will stillprotect the blade (55) underneath.

In an embodiment of the invention, the first overlap portion (4 a)tapers at least partly towards the root end (4) of the first protectivecover (1) and the second overlap portion (2) tapers at least partlytowards the tip end (3) of the second protective cover (2). Such atapered overlap portion will easier forgive any mounting variances.

In a further embodiment of the invention, each of the first overlapportion (1) and the second overlap portion (2) comprises at least onestep (5).

In yet a further embodiment of the invention, the step (5) is at leastpartly rounded.

According to another embodiment of the invention, one of the first andsecond protective covers (1, 2) comprises a protruding element (6) inthe respective first or second overlap portion (4 a, 3 a) and the otherone of the first and second protective covers (1, 2) comprises a recess(7) in the other respective first or second overlap portion (4 a, 3 a),

wherein the recess (7) is arranged to accommodate the protruding element(6). Allows for guiding the covers when being mounted.

According to another embodiment of the invention, the recess (7) may bea hole and the protruding element (6) may be nipple-shaped.

According to a further embodiment of the invention, at least one of theprotective covers (1, 2) comprise an Elastomer, e.g. comprisingPolyurethane or Polyethylene, preferably a Polyurethane based Elastomer.

Each of the first and second protective covers (1, 2) comprises fourcorners (8). At least one of these corners (8) may be rounded. A roundedcorner prevents the corner of the respective protective cover frompeeling off.

According to yet a further embodiment of the invention,

the first and second protective covers (1, 2) are

pre-formed into a curved shape in a lateral direction and

extend from their tip end (3) to their root end (4) in a longitudinaldirection, wherein at least one of the first and second protectivecovers (1, 2) has a centerline (C) running in the longitudinaldirection, and this centerline is curved such that the first and secondprotective covers (1, 2) have a sagitta height (Hp).

According to another embodiment of the invention, the first and secondprotective covers (1, 2) are pre-formed into a curved shape in a lateraldirection and extend from their tip end (3) to their root end (4) in alongitudinal direction,

wherein each of the first and second protective covers (1, 2) has acenterline (C) running in the longitudinal direction, and a first outeredge (9 a) and a second outer edge (9 b), both running in parallel tothe centerline (C). The first and second protective covers (1, 2) have athickness along their centerline (C) which tapers off towards therespective first and second outer edges (9 a, 9 b).

Avoiding peeling off of covers.

According to a further embodiment of the invention, the first and secondprotective covers (1, 2) are pre-formed into a curved shape in a lateraldirection and extend from their tip end (3) to their root end (4) in alongitudinal direction,

wherein at least one of the first and second protective covers (1, 2) iscurved in the longitudinal direction and/or tapers in the longitudinaldirection, preferably towards its tip end (3). Advantage: This avoidsthat the protective covers wrinkle when mounted to a blade. The taperingalso avoids peel-off of the protective cover and provides for acontinuous transition between the protective covers.

According to another embodiment of the invention, a length of at leastone of the first and second protective cover (1, 2) amounts to about2000 mm at maximum, preferably to about 1000 mm. Advantage: This avoidsthat the protective covers wrinkle when mounted to a blade. The taperingalso avoids peel-off of the protective cover and provides for acontinuous transition between the protective covers.

According to a further embodiment of the invention, at least one of thefirst and second protective cover (1, 2) comprises a printed centerline(C) on its outer surface (11) to facilitate the mounting onto a leadingedge (59) of a wind turbine blade (55). This facilitates the alignmentof shells and enables a quality check by optical means as well as allowsfor documenting quality-related information, e.g. photographs.

The wind turbine blade (55) according to the present invention comprisesa protective cover system (10) which is connected to the wind turbineblade (55) along a leading edge (59) of the blade (55). An advantagethereof is that less repair work is needed and the maintenance costs arereduced. In addition, a combination with a de-icing or LPS is possiblebecause of the electrical insulation property of the covers 1, 2.

The method for mounting a protective cover system (10) according to thepresent invention comprises the steps of:

-   -   Providing a wind turbine blade (55), the protective cover system        (10) according to one of claims 1-13 and an adhesive;    -   Applying the adhesive on the wind turbine blade (55) and/or on        an inner surface (12) of the first and the second protective        covers (1, 2);    -   Placing the first protective cover (1) onto the wind turbine        blade (55); and    -   Placing the second protective cover (2) onto the wind turbine        blade (55), wherein the first and the second overlap portions (4        a, 3 a) of the protective covers (1, 2) are arranged such that        the first and the second overlap portions (3 a, 4 a) overlap;    -   Optionally, applying further adhesive between the first and the        second overlap portions (4 a, 3 a); and    -   Allowing the adhesive to firmly connect the first and the second        protective covers (1, 2) to the wind turbine blade (55).

An embodiment of the invention comprises a protective cover system (10)according to claim 1 further comprising

-   -   a first set of protective covers, each of the protective covers        of the first set of protective covers corresponds to a true copy        of said first protective cover (1),    -   a second set of protective covers, each of the protective covers        of the second set of protective covers corresponds to a true        copy of said second protective cover (2),    -   a protective tip cover, and    -   a protective root cover.

Possible for some blades—first set true copy of second set!—Depending onshape and/or shorter length;

depending on repair length

Another embodiment of the invention comprises a protective cover systemaccording to claim 6, wherein the LE radius of the first protectivecover (1) is different from the LE radius of the second protective cover(2).

bending rate->LE radius

more open curvature vs., more closed curvature

only 4 diff cover types->

A further embodiment of the invention comprises a protective coversystem according to claim 6 or 7, wherein the first protective cover (1)has a chord length between 0.5 (2 m from tip/1 m-3 m) and 1.3 (12 m fromtip/pref. 9-24 m/more pref. 10-14 m) meters and the second protectivecover (2) has a chord length of about 1.3 meters or more.

Outer ⅓ (−½ to) of the length of LE −50%/50% for diff sets of shells

A further embodiment of the invention comprises a protective coversystem according to claim 6 or 7, wherein the first protective cover (1)has a chord length between 0.5 and 1.3 meters and the second protectivecover (2) has a chord length of about 1.3 meters or more.

Another embodiment of the invention comprises a protective cover systemaccording to anyone of claims 6 to 8, wherein the protective tip coverhas a swept end to cover and fit the blade tip.

Pre-bend—more curved than other shells

not exact copy of blade tip but more curved—so it is stretched whenmounted to the blade

Valid for all shells, but more exaggerated for tip shell

Tip covered or not covered/

open tip—easier fit to all variations of blade tips, but less erosionprotection performance than closed one

close tip—better protection, but requires little variance in blade tipstherefore more shell variants are needed

Another embodiment of the invention comprises a protective cover systemaccording to anyone of claims 6 to 9, wherein the protective root coverfeatures a smooth transition towards the leading edge on the root side.

-   -   root end w/o overlap portion, w/o pin hole

smooth transition towards the leading edge on the root side

Option: root shell is same as first set of shells

Advantages:

for claim 6

Compared to a rigid protection shell that can be only mounted on apredefined part of the leading-edge surface, the material of which theprotective covers according to the present invention are built has acertain flexibility which allows their mounting along a much greatersurface area along the leading-edge. As a result, the total number ofindividually designed protective covers can be reduced to a strictminimum. The resulting economic advantages with respect to productioncosts and logistic are quite obvious and important. Since in many cases,the surface shape along the leading-edge of a wind turbine blade changesonly smoothly, it's even possible to use just two different sets ofprotective covers, plus a protective tip cover and a protective rootcover. It is even possible to do with just two one set of protectivecovers, plus a protective tip cover.

for claim 7:

As stated before, the surface shape, and more precisely the leading edgeradius, along the leading-edge of a wind turbine blade changes onlysmoothly. Therefore, the same manufacturing process can be used to buildthe protective covers of the different sets. Same 3D-mould may be usedfor multiple blades types. This is be advantageously used to reducefurthermore the associated production costs.

FIG. 1 shows a wind turbine (prior art)

FIG. 2 shows a plan view of a wind turbine blade (prior art)

FIG. 3 shows the profile of a wind turbine blade together with theprotective cover system according to the invention

FIG. 4 shows a cross-sectional view of a protective cover according tothe invention

FIG. 5 to 22 showing further embodiments of the invention.

FIG. 23 shows how flexible the protective covers 1 and 2 may be

A “wind turbine rotor blade” may also be referred to as “wind turbineblade”. A “protective cover” for protecting a leading edge of a windturbine blade from erosion may also be referred to as “shell” or“shield”.

The “protective cover” according to the present invention is preformed.The protective cover is brought into a curved shape before beingmounted. It may be machined. Preferably, it is pre-casted. The term“preformed” may also be referred to as pre-shaped. According to thepresent invention, the “protective cover” is pre-shaped into a curvedshape so as to accommodate at least a part of a wind turbine blade (55).The “curved shape” referred to in claim 1 may also be described as achannel-like shape or as a substantially parabolic channel.

It is known in the art to cast a male part on the blade by use of a malemould. The resulting bond may be of superior quality. In contrast tothis concept, a female mould may be used in addition to the male mouldto pre-cast the first and second protective covers (1, 2) instead ofcasting over the blade (55) with one or more protective covers (1, 2).

Covers of an Elastomeric Polyurethane are preferred. This may be arubbery, elastic and flexible material to allow the protective shell tobe easily form-fitted to a wind turbine blade surface and to provide itwith sufficient elasticity so as to dampen the impact of erosiveinfluences.

The protective cover may be flexible. In other words, it may have someflexibility. That means the protective cover may be flexible in such away that it is less flexible than a tape but more flexible than a stiffcomponent. The advantage of a preformed but flexible protective cover ison the one hand a curved shape which facilitates handling of the coverand provides for a good fit to a curved surface, and on the other handthe fact that the protective cover may easily adapt to a range ofdifferently curved surfaces, e.g. at different locations along a leadingedge of a wind turbine blade. In other words, a preformed and flexibleprotective cover, e.g. made of a Polyurethane based Elastomer, may adaptto different curved surfaces having a range of different bending rates(angle) in a predetermined range of bending rates.

In order to keep the protective covers (1, 2) on the blade 55 even afterbeing struck by a relatively large foreign object, such as a bird or anice fragment, without a protective cover (1, 2) peeling off, theprotective cover system (10) is bonded to the blade (55), e.g. by meansof a heat-activatable adhesive. In so doing, the adhesive may be heated,e.g. by a heating blanket or a vacuum heating blanket.

FIG. 1 shows a typical wind turbine (51) comprising a tower (52), anacelle (53), a generator (56), and blades (55). The blades (55) areattached to a hub (54). They capture the energy of the wind, spinning agenerator (56) in the nacelle (53). The tower (52) comprises theelectrical conduits, supports the nacelle (53), and provides access tothe nacelle (53) for maintenance.

FIG. 2 shows a plan view of a wind turbine rotor blade (55) comprising atip (57) and a root (58), a leading edge (59) and a trailing edge (60).The rotor blade (55) further comprises a shoulder (61) near the bladeroot (58) and an airfoil portion (62).

FIG. 3 shows the profile of a wind turbine rotor blade (55) including aleading edge (59), a trailing edge (60) as well as the suction and thepressure sides (65, 64) between the leading and the trailing edges (59,60). The profile shown in FIG. 3 further comprises a protective coversystem (10) according to the present invention which is positioned alongthe leading edge (59) of the rotor blade (55).

FIG. 4 The protective cover system (10) for protecting a leading edge(59) of a wind turbine blade (55) from erosion comprises a firstprotective cover (1) and a second protective cover (2). The first andthe second protective covers (1, 2) comprise a polymer material. Thecovers (1, 2) are pre-formed into a curved shape so as to accommodate atleast a part of a wind turbine blade (55), especially along the leadingedge (59) of the blade (55).

FIG. 5 Each of the first and second protective covers (1, 2) has a tipend (3) and a root end (4). The first protective cover (1) comprises afirst overlap portion (4 a) at the root end (4) and the secondprotective cover (2) comprises a second overlap portion (3 a) at the tipend (3 a). The shape of the first overlap portion (4 a) at the root end(4) of the first protective cover (1) is substantially complementary tothe shape of the second overlap portion (3 a) at the tip end (3) of thesecond protective cover (2) such that when overlapping these first andsecond overlap portions (4 a, 3 a), the resulting cross section of theoverlapped overlap portions (4 a, 3 a) substantially correspond to thecross sections of at least one of the first and second protective coversoutside the overlap portions.

The wind turbine blade comprises a protective cover system according tothe invention, wherein the protective cover system is connected to thewind turbine blade along a leading edge of this blade.

The method for mounting a protective system to a leading edge 59 of awind turbine rotor blade 55 from erosion,

the method comprises the steps of:

-   -   Providing a wind turbine blade, a first and a second protective        covers according to the invention, and an adhesive;    -   Applying the adhesive on the wind turbine blade and/or on an        inner surface of the first and second protective covers;    -   Placing the first protective cover onto the wind turbine blade;    -   Placing the second protective cover onto the wind turbine blade,        wherein the step of placing the second protective cover onto the        wind turbine blade involves arranging the first and second        overlap portions such that these first and second overlap        portions overlap;    -   Optionally, applying further adhesive between the first overlap        portion and the second overlap portion; and    -   Allowing the adhesive to firmly connect the first and second        protective covers to the wind turbine blade.

The invention is directed towards having a plastic shell 1, 2 that isbonded to the outer surface of the blade 55, more specific of theleading edge 59. The shell 1, 2 is referred herein to as protectivecover 3. It may have a width W of +/−100 mm with respect to the leadingedge 59 of the wind turbine blade 55, see FIG. 3.

The shell may be made of a polymer comprising polyurethane and a furthercomponent. The shell is a curved protective plate in the shape of aparabolic channel. It is designed to be mounted lengthwise along theleading edge of a wind turbine blade. The shell is moulded in a mouldingprocess. The shell is pre-moulded but still pliable enough to provide atight fit to the turbine blade.

The shell system comprises a first shell and a second shell. Each shellhas two short edges, herein also referred to as tip end and root end (3,4) and two long edges, herein also referred to as outer edges. The longedges are longer than the short edges. The first short edge 4 is locatedat one end of the parabolic channel, and the second short edge 3 islocated at the opposite end of the parabolic channel. The two long edges9 are perpendicular to the two short edges 3, 4.

The shell has a centerline C running lengthwise along the substantiallyparabolic channel in parallel to the long edges 9. The thickness Tn ofthe shell is greatest along the centerline C and gradually diminishestoward the two long edges 9. The thickness Tn may be 3 mm at thecenterline C, see FIG. 4

Overlap section: A shell system comprises at least two ofabove-mentioned shells 1, 2 touching one another at their short edges 3,4. The shells may be connected to each other or interconnected byvarious means, e.g. by edge chamfer and guiding nipple 6, see FIG. 5.

The overlap portions 3 a, 4 amay have a length Lo of 30 mm inlongitudinal direction of the protective cover 1, 2. The protrusion 6may have a diameter Dp of 2 mm and the recess 7 may also have diameterDr of 2 mm. The length Lp of the protrusion may be 3 mm, see FIG. 7.

The shells may be interconnected by means of connecting elements 5, 20,21 that serve for a guiding/connecting of the two shells 1, 2.Mechanical Interlocking between the shells 1, 2 is achieved by havingconnecting elements 5, 20, 21 that have a nipple shape. This shapereduces stress concentration for the connecting element 5, 20, 21.

Transition consideration: Camfered interna—no exposure for the blade.Stepwise decline transition—provide thickness and strength which prolongthe lifetime.

Different decline transitions at different positions of the leading edgeare possible, e.g. step-like connecting elements 5 at the leading edge(that means at the Centerline C) of the shell 1, 2), step-likeconnecting elements 20 having rounded edges onto a width of the shell of+/−50 mm from the Leading edge (Centerline C) and tapered connectingelements 21 from +/−50 mm on to a width of +/−100 m (that means untilthe outer edges 9, 9 a, 9 b), see FIG. 5 and FIG. 6.

The blade chord length is decisive of the aerodynamic property—thereforeit needs to be as thin as possible. The thickness Tne at an end 4 of theshell may be around 0.05 mm. Corner rounding of corner 8 with a radiusR5 help avoiding peeling off of the shell, see FIG. 7a

At an end 3, 4 in lengthwise direction of the shell, the overlap area 3a, 4 amay have a length of 20-40 mm, preferably 30 mm. The thickness ofthe shell may diminish in the overlap area to a very small thickness inthe range of 0.03 mm to 0.07 mm, preferably to about 0.05 mm.

The shell may have a peel height Hp, referred to in Danish language asPeelhejde (in English language Sagitta height). That means the shell 1,2 may be curved with a radius R2, that means the centerline C is curved.see FIG. 8.

It is from other technology to extrude plastic elements. This inventionis directed towards overcoming the disadvantage of having an extrudeelement.

Having a sagitta height Hp enables the shells to be drapable. The heightdifference between an outer end of the shell and a position at thecenterline in the middle of the shell may be 3 to 7 mm, preferably about5 mm.

The sagitta height Hp is achieved during the manufacturing of the shell.Each of the shells will be moulded as one piece. Another advantage ofcasting the shells is that each shell can be tailored.

The protective cover system 10 comprising a first and a secondprotective cover 1, 2 (first and second shell) may have an open angle atthe Overlap OV. That means the angle between centerline C and root ortip end 3, 4 is smaller than 90 degrees and the angle between outer edge9 and root or tip end 3, 4 is greater than 90 degrees. At the outer edge9 the distance Dd may be 3 mm, see FIG. 9.

Each overlap influences the aerodynamic performance of the blade. It isimport to avoid excess overlap and thereby material. Therefore theoverlap is less than 30 mm.

Bondline Features: Indentation, e.g with 20 mm spacing inbetween theindentations, on the inner surface ensure a better bonding due to thefact that the indentation entrap glue, see FIG. 10

A tailored tip as shown in FIG. 11 may have a length Lt in the range ofaround 530 mm to 630 mm, a width Wt1 of around 50 mm at the tip end 3 ofthe shell 1 and a width Wt1 of around 100 mm at the root end 4 of theshell 1. In addition, at the tip end 3 of the shell 1 Wt1 may beslightly greater such that a Radius R30 is generated at the outer edgeof the shell. So, the tip of the blade is very good enclosed and thusprotected from erosion, see FIG. 11 showing a tip shell (soft tip shell)

Enclosing the tip of the blade is an option, as also shown in FIG. 12.Better transition of the tip. One unique shell could be used for the tipend.

As an alternative, the tip shell 1, may be designed to leave the tip ofthe blade 30 blank, that means not covered, see FIG. 12.

Advantages

-   -   Compared to coating and tape solutions this invention offers a        method that can be done in one working step    -   Having a peel height enables the shells to be drapable. The peel        height is achieved during the manufacturing of the shell. Each        shell will be moulded as one piece.    -   Another advantage of casting the shells is that each shell can        be tailored    -   Cost and repair reduced

Further Aspects of Invention

The length of at least one of the first and second protective cover (1,2) may amount to about 2000 mm at maximum, preferably to about 1000 mm.

Advantage: good length blade, in view of operational window (1.7 m). w/orepositioning worker himself

Method for mounting a protective cover system (10) according to one ofclaims 1-4 to a leading edge (59) of a wind turbine blade (55),

the method comprises the steps of:

-   -   Providing a wind turbine blade (55), the protective cover system        (10) according to one of claims 1-13 and an adhesive;    -   Applying the adhesive on the wind turbine blade (55) and/or on        an inner surface (12) of the first and the second protective        covers (1, 2);    -   Placing the first and the second protective covers (1, 2) onto        the wind turbine blade (55), wherein the first and the second        overlap portions (4 a, 3 a) of the protective covers (1, 2) are        arranged such that the first and the second overlap portions (3        a, 4 a) overlap;    -   Optionally, applying further adhesive between the first and the        second overlap portions (4 a, 3 a); and    -   Allowing the adhesive to firmly connect the first and the second        protective covers (1, 2) to the wind turbine blade (55).

The protective cover system (10) according to claim 1 further comprising

-   -   a first set of protective covers, each of the protective covers        of the first set of protective covers corresponds to a true copy        of said first protective cover (1),    -   a second set of protective covers, each of the protective covers        of the second set of protective covers corresponds to a true        copy of said second protective cover (2),    -   a protective tip cover, and    -   a protective root cover.

Possible for some blades—first set true copy of second set!—Depending onshape and/or shorter length;

depending on repair length

The protective cover system according to claim 6, wherein the LE radiusof the first protective cover (1) is different from the LE radius of thesecond protective cover (2).

bending rate->LE radius

more open curvature vs., more closed curvature

only 4 diff cover types->

The protective cover system according to claim 6 or 7, wherein the firstprotective cover (1) has a chord length between 0.5 (2 m from tip/1 m-3m) and 1.3 (12 m from tip/pref. 9-24 m/more pref. 10-14 m) meters andthe second protective cover (2) has a chord length of about 1.3 metersor more.

Outer ⅓ (−½ to) of the length of LE −50%/50% for diff sets of shells

The protective cover system according to claim 6 or 7, wherein the firstprotective cover (1) has a chord length between 0.5 and 1.3 meters andthe second protective cover (2) has a chord length of about 1.3 metersor more.

The protective cover system according to anyone of claims 6 to 8,wherein the protective tip cover has a swept end to cover and fit theblade tip.

Pre-bend—more curved than other shells

not exact copy of blade tip but more curved—so it is stretched whenmounted to the blade

Valid for all shells, but more exaggerated for tip shell

Tip covered or not covered/

open tip—easier fit to all variations of blade tips, but less erosionprotection performance than closed one

close tip—better protection, but requires little variance in blade tipstherefore more shell variants are needed

The protective cover system according to anyone of claims 6 to 9,wherein the protective root cover features a smooth transition towardsthe leading edge on the root side.

-   -   root end w/o overlap portion, w/o pin hole

smooth transition towards the leading edge on the root side

Option: No root shell

Advantages

for claim 6

Compared to a rigid protection shell that can be only mounted on apredefined part of the leading-edge surface, the material of which theprotective covers according to the present invention are built has acertain flexibility which allows their mounting along a much greatersurface area along the leading-edge. As a result, the total number ofindividually designed protective covers can be reduced to a strictminimum. The resulting economic advantages with respect to productioncosts and logistic are quite obvious and important. Since in many cases,the surface shape along the leading-edge of a wind turbine blade changesonly smoothly, it's even possible to use just two different sets ofprotective covers, plus a protective tip cover and a protective rootcover. It is even possible to do with just two one set of protectivecovers, plus a protective tip cover.

for claim 7:

As stated before, the surface shape, and more precisely the leading edgeradius, along the leading-edge of a wind turbine blade changes onlysmoothly. Therefore, the same manufacturing process can be used to buildthe protective covers of the different sets. Same 3D-mould may be usedfor multiple blades types. This is be advantageously used to reducefurthermore the associated production costs.

1. Protective cover system (10) for protecting a leading edge (59) of awind turbine rotor blade (55) from erosion, the system (10) comprising afirst protective cover (1) and a second protective cover (2), bothcomprise a polymer and being pre-formed into a curved shape so as toaccommodate at least a part of a wind turbine rotor blade (55) to beprotected, each of the first and second protective covers (1, 2) has atip end (3) and a root end (4), wherein the first protective cover (1)comprises a first overlap portion (4 a) at the root end (4), and thesecond protective cover (2) comprises a second overlap portion (3 a) atthe tip end (3), wherein the shape of the first overlap portion (4 a) issubstantially complementary to the shape of the second overlap portion(3 a) such that when overlapping the first and second overlap portions(4 a, 3 a), the resulting cross section of the overlapped overlapportions (4 a, 3 a) substantially corresponds to the cross sections ofat least one of the first and second protective covers (1, 2) outsidethe overlap portions (4 a, 3 a).
 2. The protective cover system (10)according to claim 1, wherein the first overlap portion (4 a) tapers atleast partly towards the root end (4) of the first protective cover (1),and the second overlap portion (2) tapers at least partly towards thetip end (3) of the second protective cover (2).
 3. The protective coversystem (10) according to claim 1 or claim 2, wherein each of the firstoverlap portion (1) and the second overlap portion (2) comprises atleast one step (5).
 4. The protective cover system according to claim 3,wherein the step (5) is at least partly rounded.
 5. The protective coversystem (10) according to one of claims 1-4, wherein one of the first andsecond protective covers (1, 2) comprises a protruding element (6) inthe respective first or second overlap portion (4 a, 3 a), and whereinthe other one of the first and second protective covers (1, 2) comprisesa recess (7) in the other respective first or second overlap portion (4a, 3 a), wherein the recess (7) is arranged to accommodate theprotruding element (6).
 6. The protective cover system (10) according toclaim 5, wherein the recess (7) is a hole and the protruding element (6)is nipple-shaped.
 7. The protective cover system (10) according to oneof the preceding claims, wherein at least one of the protective covers(1, 2) comprise an elastomer, e.g. comprising Polyurethane,Polyethylene, polyaspartic (proposed by Covestro) (?).
 8. The protectivecover system (10) according to one of the preceding claims, wherein eachof the first and second protective covers (1, 2) comprises four corners(8), wherein at least one of these corners (8) is rounded.
 9. Theprotective cover system according to one of the preceding claims,wherein the first and second protective covers (1, 2) are pre-formedinto a curved shape in a lateral direction and extend from their tip end(3) to their root end (4) in a longitudinal direction, wherein at leastone of the first and second protective covers (1, 2) has a centerline(C) running in the longitudinal direction, the at least one of the firstand second protective covers (1, 2) further comprises an outer edge (9),the outer edge (9) running in parallel to and being shorter than therespective centerline (C).
 10. The protective cover system (10)according to one of the preceding claims, wherein the first and secondprotective covers (1, 2) are pre-formed into a curved shape in a lateraldirection and extend from their tip end 3) to their root end (4) in alongitudinal direction, wherein each of the first and second protectivecovers (1, 2) has a centerline (C) running in the longitudinaldirection, and a first outer edge (9 a) and a second outer edge (9 b),both running in parallel to the centerline (C), wherein the first andsecond protective covers (1, 2) have a thickness along their centerline(C), wherein the thickness tapers off towards the respective first andsecond outer edges (9 a, 9 b).
 11. The protective cover system (10)according to one of the preceding claims, wherein the first and secondprotective covers (1, 2) are pre-formed into a curved shape in a lateraldirection and extend from their tip end (3) to their root end (4) in alongitudinal direction, wherein at least one of the first and secondprotective covers (1, 2) is curved in the longitudinal direction and/ortapers in the longitudinal direction, preferably towards its tip end(3). Advantage: avoid shell wrinkle tapering: avoiding peel-off,continuous transition between shells
 12. The protective cover system(10) according to one of the preceding claims, wherein a length of atleast one of the first and second protective cover (1, 2) amounts toabout 2000 mm at maximum, preferably to about 1000 mm.
 13. Theprotective cover system (1, 2) according to one of the preceding claims,wherein at least one of the first and second protective cover (1, 2)comprises a printed centerline (C) on its outer surface (11) tofacilitate the mounting onto a leading edge (59) of a wind turbine blade(55).
 14. Wind turbine blade (55) comprising a protective cover system(10) according to one of the preceding claims, wherein the protectivecover system (10) is connected to the wind turbine blade (55) along aleading edge (59) of the blade (55).
 15. Method for mounting aprotective cover system (10) according to one of claims 1-13 to aleading edge (59) of a wind turbine blade (55), the method comprises thesteps of: Providing a wind turbine blade (55), the protective coversystem (10) according to one of claims 1-13 and an adhesive; Applyingthe adhesive on the wind turbine blade (55) and/or on an inner surface(12) of the first and the second protective covers (1, 2); Placing thefirst and the second protective covers (1, 2) onto the wind turbineblade (55), wherein the first and the second overlap portions (4 a, 3 a)of the protective covers (1, 2) are arranged such that the first and thesecond overlap portions (3 a, 4 a) overlap; Optionally, applying furtheradhesive between the first and the second overlap portions (4 a, 3 a);and Allowing the adhesive to firmly connect the first and the secondprotective covers (1, 2) to the wind turbine blade (55).
 16. Theprotective cover system (10) according to claim 1 further comprising afirst set of protective covers, each of the protective covers of thefirst set of protective covers corresponds to a true copy of said firstprotective cover (1), a second set of protective covers, each of theprotective covers of the second set of protective covers corresponds toa true copy of said second protective cover (2), a protective tip cover(?), and a protective root cover (??).
 17. The protective cover systemaccording to claim 16, wherein the LE radius of the first protectivecover (1) is different from the LE radius of the second protective cover(2).
 18. The protective cover system according to claim 16 or 17,wherein the first protective cover (1) has a chord length between 0.5 (2m from tip/1 m-3 m) and 1.3 (12 m from tip/pref. 9-24 m/more pref. 10-14m) meters and the second protective cover (2) has a chord length ofabout 1.3 meters or more.
 19. The protective cover system according toclaim 16 or 17, wherein the first protective cover (1) has a chordlength between 0.5 and 1.3 meters and the second protective cover (2)has a chord length of about 1.3 meters or more.
 20. The protective coversystem according to anyone of claims 16 to 19, wherein the protectivetip cover (?) has a swept end to cover and fit the blade tip.
 21. Theprotective cover system according to anyone of claims 16 to 20, whereinthe protective root cover (??) features a smooth transition towards theleading edge on the root side.